Mr.D-'97 A4q 12v

should give me the best mileage? For some reason this is backwards from what I would have expected.

With the increasing gas prices, I'm trying to come up with a way to increase my mileage.

I have the original four o-ring sizes but I can't find the 5th one with the largest ID. I am currently running the one with the 2nd largest ID. Before I found this post, I was gonna swap in the one with the largest ID, if I found it.

Thanks!<ul><li><a href="https://forums.audiworld.com/12v/msgs/24132.phtml">https://forums.audiworld.com/12v/msgs/24132.phtml</a</li></ul>

VAP

which is either no o-ring or the skinniest/largest internal diameter o-ring.

O-rings reduce the orifice internal diameter which increases velocity across the sensor wires the same way a garden hose hand nozzle does when you restrict water output to a jet stream, ie; high velocity. But there is some reduction in volume. However the MAF can only sense velocity and is completely oblivious to volume and has no provision whatever to determine volume. Increased velocity tricks the sensor into believing more air volume is entering and therefore more fuel is sent to the combustion chambers. Slower velocity (larger opening) tricks the sensor into sending less fuel and thats why people with old, bad or faulty O2 sensors start to get lean codes when running no o-ring.

If you can run code-free with no o-ring that will give you the best fuel economy. Literally 100% of people with "good" O2 sensors can do this and remain code-free. If a code occurs then try the largest ID/skinniest cross-section o-ring. If that produces a code then go to the next one up which is the most popular and closest to a stock/unmodified MAF equivalent. If that throws a code there is another problem elsewhere.

rtking

I changed my O2 and would love to get better mileage in my awful stop-and-go commute. I forgot that I could remove the O-Ring and, in return, get a little more power from running leaner. I now have a morning project! :-)

Mr.D-'97 A4q 12v

Thanks, Mance. That's what I was thinking but wanted to make sure.

AlwaysAudi

Hey Mance do you have any EFK around?